SOMETIMES, favorable newspaper exposure is not a good thing. Michael Psilakis and Donatella Arpaia, owners of Greek restaurant Kefi on Columbus Avenue, were shocked yesterday when the city’s Health Department shut it down after a month of land-rush business. The out-of-the-blue closure came the same day as a rave writeup by The Post’s Steve Cuozzo. Arpaia and Psilakis – who’ve never had a problem with any of their other restaurants, including Mia Dona and Michelin-starred Anthos – “were found operating without a permit and a food protection course certificate holder present,” the Health Department claimed. Psilakis said it was essentially a paperwork problem and would be corrected promptly, but it was unclear whether Kefi would reopen in time for lunch or dinner today.